Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

Background. The paper presents the relationships between relative and absolute length of the crowns of trees in Kraft biosocial classes, in the investigated 56-year-old oak stand, taking into account the length of the sun- drenched and shaded parts.

Material and methods. The measuring material was collected on the 0.46 ha plot of an oak stand in the Zielonka Experimental Forest District. In accordance with the criteria of Kraft classes the biosocial position was established for each tree. For standing trees the diameter at breast height was measured in the tree bark in the two directions of the N–S and E–W with an accuracy of 0.1 cm, as a result of this measurements   the arithmetic mean was assumed as the diameter at breast height (d1.3). The tree height (h), height of base of live crown to the first living branch as the basis of the compact crown were measured. Moreover, the height of the widest diameter at breast height which separates the sun-drenched and shaded parts of tree was  established.

The crown length lk of trees growing in the stand was calculated as the difference between the tree height and the height of the base of live a crown, while the length of sun-drenched crown lks as the difference between the tree height and the height of the widest diameter of the crown. The length of the shaded tree crown lkc was calculated as the difference between the height of the widest diameter of the crown and the height of hebase of a live crown. The relative length of the crown lk/h was calculated as the quotient of the length of the tree crown with reference to the tree height, while the share of sun-drenched and shaded parts of crowns with reference to the crown length.

Results. It was concluded that the mean absolute and relative length of the crowns had a downward trend with decreasing biosocial position of trees. Similarly, the length of the sun-drenched and shaded crown was a decreasing with the a decrease of Kraft classes. In contrast, relations between the relative share of sun- drenched and shaded parts of oak crowns were formed in a different manner. The biosocial position of trees did not affect the share of these parts in the crown. The ratio of the length of the sun-drenched to the shaded part of crown in the crown length was 4 to 6.